Power transmission



1 Aug. 8, 1939.A E. ROSE ET A'L 2,168,656

POWER TRANSMISSION Fi11 Feb. 16, '1937 e sheetssheet 1 INVENTOR Enw//v ..Ross

RALPH L TwEEvALE ATTORNEY Aug., 8, 1939. E. L. ROSE ET AL Powa TRANSMISSION Filed Feb. 1e, 193'/ 6 sneets-sneet 2 INVENTORS EDWIN L. ROSE .Q BY RALPH L. TWEEDALE ATTORNEY Allg 8, 1939- E. L, RosE E-r AL POWER TRANSMISSION 6 Sheets-Sheet 4 Filed Feb.. 16, 1957 E L. o a

R H L. EEDALE ATT ORNEY Aug- 8, 1.939. E. L. Rosa ET A1. 2,168,656 6 POWER ,TRANSMISSION Filed Feb. 16, 1937 6 Sheets-Shea?l 6 l I0 /63 /OlNvENToRs EDWIN L. Rose BY RALPH L..TWEEDALE ATTORNEY Patented Aug. 8, 1939 2,168,656 n PoWER TRANSMISSION Edwin L. Rose, Watertown, and Ralph L. Tweedale, Waterbury, Conn., assignors to The Waterbury Tool Company, Waterbury, Conn., a corporation of Connecticut Application February 16, 1937, serial No. 126,022

12 claims. (c1. 74-283) This invention relates to power transmissions, particularly those of the variable ratio type wherein a driving member and a driven member may be connected together at different speed cient eifort to operate the control of the innite transmission. Likewise, in many other applications, such as price indicating gasoline pumps, it is desirable to have a compact gear set v ratios. Variable ratio transmissions are of two Which provides selectively a-large number of 5 general classes; one of which is the positive drivratios. ing type, such as a change speed gear box; the It is also an object to provide a transmission other of which is the innite ratio type exempliof the type described Wherein the ratio setting fied by the well-known hydraulic, friction or elecmay be controlled by progressive equal steps tric transmissions. The positive type presents through the operation of a single rotary shaft, 10 the advantage that the speed ratio at any parpreferably one which partakes of a large numticular setting of the transmission is absolutely ber of revolutions in covering its full range. A fixed and ,unvarying regardless of loading condidevice of this character is valuable in computing tions and other variable factors. They have a machines since it may serve to provide a continudisadvantage, however, that it is difficult to proous product of two variable velocities. 15

Vide 2 large number 0I" ratio settings Without These objects are achieved by the provision of making the device extremely large, complicated, a multiple speed gear set which comprises a pluexpensive and ine'icient. The innite ratio type rality of planetary differential gears connected provides a completely step-less change in ratio so in series; that is, the input member of each difthat the device may be set to provide any speed ferential may be connected to the output mem'- 20v ratio WhatSOeVeI Within its range 0f operation. ber of the next adjacent differential or stage. It is impossible, however, to maintain a given The third or control member of each differential ratio setting with absolute accuracy under varymay be driven at any one of several ratios from ing load and other conditions which eiect the the input shaft or may be held stationary, the slippage of the transmission. overall ratio being determined by the combined 25 v In many power transmission applications a effects of the particular ratios of the control large number of speed ratios must be available member of the diierential at each stage. and this necessitates the use of an innte ratio By analogy to the theory of numbers the structype of transmissions; since a positive type, proture may be considered in certain aspects as a 'viding a sufiicient number of ratios, would be mechanical number system and may be con- 30 entirely unfeasible. With the iniinite ratio type structed upon any base number, which, of course, it is difficult to maintain absolute constancy of is the number of digits in the system,`including speed ratio at any setting so that it is necessary zero. For convenience the form of the invento adjust the transmission setting by trial and tion chosen for illustration is based on the decierror whenever it is necessary .to change the mal system; that is, in which the base number is 35 ratio, and a frequent check on the setting must 10, although it will be understood that the prinbe made during operation. ciples involved may be incorporated in transmis- The present invention is concerned Withapowsions built upon a system having a larger or ,er transmission of the positive type in which the smaller base number. v 40 number of ratios available is iinite but so large While it has been proposed heretofore to use 40 as to be, for all practical purposes, infinite; in differential gears to add together the outputs of other words, to provide for changing the ratio a plurality of variable ratio gear sets, such as by the smallest steps which would ever be rethe common cone cluster gears, in a manner to quired in a particular application. provide an arithmetical progression of speed .l5 It is an object to provide a transmission of this ratios, such a system requires the introduction 4.5 character in which the available ratios are arof a fixed multiplying gearing for each variable ranged in arithmetical progression and in which ratio gear set. The ratio of these multiplying the mechanism is arranged in compact form. gears must correspond to the Successive powers A transmission of this character, for example, of the base number; for example, in a decimal may be used as a pilot control for an infinite type gear set of such character one multip-lying gear of transmission, in which case the innite type must have a factor of one, the next one a factor transmission may be of sufficient capacity to of ten, the next one a factor of one hundred, etc. handle the entire load being transmitted while the This is objectionable not only because the multipositive transmission may be small and of light plying gears become very cumbersome if any construction capable of transmitting only sufllarge number of stages are used but also because 55 a separate driving train including the multiplier gearing and the variable ratio gearing must be provided for each stage.

By the present invention these difficulties are avoided by utilizing a planetary differential gearing in which the inherent ratio of the planetary gearing with the control member locked corresponds to the base number of the system. By properly selecting the ratios at which the control member of each stage may be driven, it is possible to provide arithmetical progression of ra-.

tios with a common set of driving trains for all stages of the device; that is, with the same multiplying factor, preferably unity, between the input or output shaft and the variable ratio gearing at each stage. These driving trains preferably comprising a set of shafts are arranged circum,` ferentially around the outside of the planetary gears, which are mounted upon a common axis, so that a compact mechanism may be provided in which the number of ratios available is equal to the base number of the system raised to a power equal to the number of differentials or stages in the gear set. For example, in a decimal system only five stages are required to produce one hundred thousand ratios with increments in output speed varying in arithmetical progression.

It is also an object to provide a variable ratio transmission of the character described in which the number of dissimilar parts is substantially reduced. By the present invention the dies and tools necessary to manufacture a transmission of only one stage are all that is necessary to manufacture a transmission having any number of stages. The parts necessary to add to provide additional stages are identical to the parts already present in the first stage except for twelve longitudinal shafts and the casing.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the ace companying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a longitudinal section through a power transmission device incorporating a preferred form of the present invention.

Fig. 2 is a transverse section on line 2 2 of Fig. l.

Fig. 3 is a transverse section on line 3 3 of Fig. 1.

Fig. 4 is a transverse section on line 4 4 of Fig. 1.

Fig. 5 is an end View of the device.

Fig. 5 is a transverse section on line 6 6 of Fig. 1.

7'ig. '7 is a cross section on line 1 1 of Fig. 6. Fig. 8 is a view corresponding to Fig. 2 showing a modified form of the present invention.

Fig. 9 is a cross section on line 9 9 of Fig. 8. Referring now to Fig. 1 there is illustrated the first and last stage mechanism of a transmission device which may have any number of additional intermediate stages, each a duplicate of those shown. The device includes a frame or casing comprising the end plates IB and I2, a bottom plate I4 and a U-shaped cover plate I6. Journalled on bearings I8 in the end plate I2 is a shaft 29 which for the purposes of the present description is considered as the input shaft, it being understood that the device may be opern ated for transmission of power in either direction therethrough. The shaft 29 forms a central support for much of the interior mechanism. Journalled on the shaft 2U are a plurality of planetary differential gear sets, each of which comprises a sleeve 22 having a pinion 24 formed on its right-hand end which comprises the sun gear of each differential. Each sleeve 22 is also formed with a three-armed spider 26 at its left-hand end forming the planet carrier for the differential next adjacent on the left. The spider 26 for the first stage, that is the one nearest plate I2, is anchored to a plate 28 secured to the plate I2 by suitable fastening means 38 and 32.

Journalled on the sleeve 22 adjacent the sun pinion 24 is a plate 34 having an internal ring gear 36 which forms the orbit gear or control member of each differential. Meshing with the orbit gear 3B and the sun pinion 24 are three planet pinions 38 which are journalled on studs 49 secured to the arms of spider 26. It will be seen that the sleeves 22 form an integral connection between the output-spider 2li-of one differential and the input-sun pinion 24 of the next differential to the right. Plate 34 is provided with gear means whereby it may be operated at any one of several speeds. In the present arrangement this means comprises two gears 42 and 44 with which various drive pinions, later to be described, may be brought into mesh.

Keyed to the shaft 29 is a main driving pinion 46 from which are driven nine driving train shafts I through 9, inclusive, which are journalled in the end plates I8 and I2. rEhe gearing for driving these shafts is illustrated in Fig. 2 from which it will be seen that, in the plane nearest the plate I2, a large gear 48 meshes with pinion 46 and is journalled on the fastening means 30 for the plate 28. Secured to the gear 48 but in the second plane from plate I2 is a pinion 50 which meshes with a pinion 52 keyed to the shaft I. Also in the rst plane is an idler gear 54 journalled on a fixed stud 56 which meshes with pinions 58 and 6I] keyed to the shafts 4 and 5, respectively. In the second plane from the plate I2 is an idler gear 62 journalled on a fixed stud 64 which meshes with pinions G8 and 68 keyed to the shafts 2 and 3, respectively. Also in the second plane is an idler gear ID journalled on a fixed stud I2 which meshes with a pinion I4 keyed to the shaft 6; and an idler gear 'I6 journalled on a xed stud "I8 meshing with a pinion B keyed to the shaft 9. In the third plane from the plate I2 is a gear 82 secured to the idler gear 'I0 and meshing with a pinion 84 keyed to the shaft 'I as well as a gear 86 secured to the gear 'I6 and meshing with a pinion 88 keyed to the shaft 8. Each of the shafts I through 9 carries a set of pinions 98 or 92 (see Figs. 1 and 3) there being a pinion on every shaft for each stage of the mechanism, the pinions 90 lying in the plane of the gear 42 on plate 34 of the differential and the pinions 92 lying in the plane of the gear 44.

The shafts I through inclusive are adapted to drive the gear 42 of any differential with a reduction ratio of one to six. The shafts 6 through 9 inclusive are adapted to drive the gear 44 of any differential with a reduction ratio of one to two. The ratio between the shaft 20 and the shafts I through 5 inclusive are arranged so that shaft I is driven at the speed of shaft 20. Shaft 2 is driven at 1% the speed of the shaft 2E). Shaft 3 is driven at 1% the speed of the shaft 20. Shaft 4 is driven at 2% the speed of the shaft 20 and shaft 5 is driven at 3% the speed of the shaft 2D. Thus, with the one to six reduction between the shafts I through 5 and the gear 42, the overall ratio between shaft 20 and gear 42 is one to nine when the shaft I is driving, two to nine when the shaft 2 is driving, three to nine when the shaft 3 is driving, etc.

Correspondingly the shaft 6 is driven from shaftv20 at a ratio of twelve to nine, the shaft I at a ratio of fourteen to nine, the shaft 8 at a ratio of sixteen to nine, and the shaft 9 at a ratio of eighteen to nine. Thus, the overall ratio between the shaft 20 and gear 44- is six to nine When the shaft 6 is driving, sevenr to nine when the shaft 1 is driving, eight to nine when the shaft 8 is'driving, and nine to nine when the shaft 9 is driving.

For the purpose of connecting the orbit gear 36 of any differential to any one of the shafts I through 9, a plurality of arms 94 are pivoted on the shafts I through 9, there being a set of arms for each differential. Each of the arms 94 carries an idler pinion 96 meshing with the corresponding pinion or 92 and which is adapted to mesh with one of the gears 42 or 44 whenever the corresponding arm 94 is moved inwardly toward the shaft 20. An arm 98 is also pivoted on a control shaft |00 journalled in the end plates I0 and I2. The arm 98 carries a detent |02 engageable with the gear 42 for the purpose of locking the same against rotation. 'Ihe arms 94 and 98 are controlled by a cam |04 having a notch |05 and which is journalled on the sleeve 22 and has rigidly secured thereto a gear |06 (see Fig. 6). Springs 95 are connected between adjacent arms 94 to hold their inner ends in contact with cam |04. v

Supported on the shafts |00 and 9 at each stage is a triangular plate |08 which carries a stud ||0 on which an idler gear ||2 is pivoted and which meshes with the cam driving pinion |06. Meshing with the gear ||2 is a gear ||4 which is rigidly secured to a sleeve I It, the latter having a drum dial ||8 formed on its right-hand end. The sleeve ||6 for the rst stage is keyed to the control shaft |00, the remainder of the sleeves being freely rotatable thereon. Secured f to each drum 8 is a one-tooth Geneva wheel this purpose a transfer pinion |22 is freely rotatable on a shaft |24 and meshes with both the Geneva wheel |20 and the gear H4. The ratio between each gear ||4 and its cam driving gear |06 is one to one. Each of the dial drums lies under a window opening |26 formed in the casing member I6 and carries numerals from zero to nine.

The output of the last stage of the device, namely the sleeve 22, is journalled in a clutch sleeve |28 which in turn is journalled on bearings I3?) in the end plate I0. Clutch sleeve |20 car-k ries an output shaft |32 and has internal splines at |34 for non-rotatably connecting the pinion 24 of the last sleeve 22 with the clutch sleeve |28.

The internal end face of the clutchsleeve |28 5) abutting against the left-hand face of flange At the upper end the shaft |44 'carries anoperating handle |48 whereby the shaft |44 and arm |46 may be rotated to move the clutch sleeve |28 to the right. Preferably a mask slide |50 is mounted beneath the windows |26 and is connected by afork arm |52 to be moved longitudinally to the left in Fig. l when the shaft |44 is rotated to disengage the clutch ISS-|38.

For the purpose of interlocking the operation of lever |48 with that of the control shaft |00 the slide |50 is provided with depending prongs |54 v adjacent each drum ||8. The drums are provided with slots |56 which are adapted to register with the prongs |54 only when drums ||8 are each in zero indicating position. A hand wheel |58 may be provided for operating the control shaft |00. In the position of the parts illustrated in Fig. 1 the control shaft lies in the zero ratio position and the clutch operating handle |48 has been moved to direct drive position wherein the control shaft 00 is locked by engagement of prongs |54 with slots |56 and wherein the input shaft 20 is directly clutched to the output shaft |32 at |36-|38. In this position of the slide |50 the openings |26 are preferably masked so that the numeral wheels cannot be read. If the clutch operating lever |48 be moved t0 clutch disengaging position the control shaft |00 is unlocked by movement of the slide |50 to the left of Fig. 1 and the input shaft is disconnected from the output shaft |32 by movement of the clutch sleeve |28 to the right.

The operation of the device to obtain various drive ratios between the shafts 20 and |32 may best be understood from a consideration of some of the principles involved in differential gearing. Considering a single planetary differential unit, such as that illustrated in Fig. fl, the ratios between any two of the three elements may be determined from the formula:

Where N1 is the speed of the input member or sun gear, N2 is the speed of the control member or orbit gear, and N3 is the speed of the output member or the planet carrier. R is a quantity one greater than the ratio between the diameter of the sun gear and the diameter of the orbit gear. R is also the base number of the system upon which the gear change box of the present invention is constructed. In the present invention the value of N2 is variable in R steps from Zero up to N1. Thus N2 may be either zero,

N1 2N1 3N1 R-l R-i R-1 etc., up to (I2-DNI R-l The stages are arranged Y. from yright to left in the table so that the N2, N20,

and N260 tabulations correspond with theunits, tens, and hundreds digits of the ratio tabulation, and thus are read in the same manner as the dials of the device described are read. N is used as the speed of the input shaft to the device as a whole.

I04nwhile'theprevious one is lifted. Thus, after nine-tenths of a revolution of shaft 100, the shaft 9 will be driving the orbit gear 36 of the rst stage at the same speed as the input shaft 20, corresponding to the third horizontal line in the above table. A further tenth revolution Stage 3 (NwFNso) Stage 2 (N10=N3) Stage l (N1=0) Ratio N300 Nao-I-QNzun N100 Nao Na-I-QNzo N20 Ns N1I9N2 N2 l 10 l0 .001 l. .G01N .GIN-I-O 0 .01N .1N-H) 0 .1N 0+N Ii .002 .002N .02N-I-O 0 02N .2N-|-0 0 .2N 0+2N 2`I\ l .009; .009N .09N-I-0 0 .09N .9N-H) 0 .9N O-I-QN N .01() .[)lON .10N-H) 0 .10N O-I-N l 0 w 0 .011 .011N .11N+0 0 .11N .1N+N E .1N 0+N 15 10 10 9 10 9 $$***YI** *ft'ifl'iraf *1** afi-#nv .019 .019N .l9N-i-0 .19N .QN-I-N .9N 0+9N N l0 ll) 9 10 .02o .ozoN .20N-1-o o .20N 0+2N 1g 0 0| 0 o .O21 .021N .2lN-I-0 0 .21N lN-I-2N 21 \I .1N U-I-N E n *HFXUYHHK* Ww-v-- .099 `09m 99N+0 o .99N 9N+9N N .9N 0+9N N .100 .100N O-I-N 0 m 0 0 O-I-O 0 K 10 9 10 1o '.1701 .101N 01N|-N` 1g 01N 1N|o o .1N 0|N E l() 9 10 l0 9 Jwwv'r 'r *#*liii* .999 .999N .99l\I+9N N .99N QN-I-QN N .9N O-l-QN N .000 0 0+() o 0 M o 0 n@ o To 10 io 1.000 N 0+0 0 0 0 -I-0 0 0 O-l-O 0 (Clutch 13G-138 en- T 10 T0` gaged.)

From this table it Will be seen that the overall ratio of the transmission device illustrated in the drawings may be determined by the settings of the cams |04 at each stage. Rotation of the hand wheel |58 turns the control shaft |00 and with it the gear II4, sleeve H6, and dial I|8, of the first stage. The cam |04 of the first stage is also rotated at one to one ratio with the hand wheel |58 through the medium of the idler gear H2. Starting from the position illustrated in Fig. 3 one-tenth revolution of the shaft |00 counterclockwise in Fig. 3 will move the cam |04 a corresponding amount so that the arm 98 is raised to release the detent |02 from gear 42 and the arm 9d which is pivoted on shaft I is permitted to fall into the notch of the cam |04 engaging the corresponding idler pinion 96 with the gear 42. In this position first stage dial IIB will read one while all other dials will remain in zero position being locked by the Geneva Wheels I and transfer pinions |22. The orbit gear is thus driven from the input shaft 20 through the pinion 46, gear 48, pinions 50 and 52, shaft I, and gearing 90, 9B, and 42 at one-ninth the speed of the input shaft 20. This setting corresponds to the first horizontal line in the table above.

If control shaft |00 be rotated further counterclockwise at each tenth revolution the next adjacent4 arm 94 drops into the notch of cam of the shaft |00 brings the transfer mechanism |20, |22, and |24 into operation rotating both the first and second stage sleeves I|6 and cams |04 through one-tenth of a revolution. This position corresponds to the fourth line of the above table. Continued rotation of the control shaft |00 actuates the cams |00 and the dials IIB in a manner exactly analogous to the conventional odometer totalizer.

It is thus possible to select any overall ratio of power transmission through the device, the ratio selected being determined by the number of revolutions imparted to the control shaft |00 and being indicated directly by the dials II8. 'Ihe control shaft 00 may be operated either forwards or backwards depending upon whether it is desired to increase the ratio from its previous adjustment or to decrease the same.

The shape of the notch in each of the cams |04 is preferably such that during any tenth of! a revolution between one ratio setting and thei next, two of the pinions 96 or one pinion 96 and the detent |02 may be engaged with the gear i2 or fifa. By this construction it is insured that the orbit vgear 36 will always be under positive control and will never be freed of connection with at least one of the driving shafts I through 9 or the detent |02. During the interval while two pinions are engaged, ring gear 36 is driven by the faster one of the two, while the other merely ratchets on its gear GZor 44 until the cam |04 reaches the next even tenth of a revolution position; that is, with only one arm 94 in the notch. The direction of rotation of the input shaft 2d and the driving shafts I through 9 is preferably clockwise in Figs. 2 and 3 whereby the swinging action of the arms 6 is partially self-energized by the driving forces of the gears S6, 92, S6, l2 and |16. This feature is not essential, however, inasmuch as the springs 95 may be made suiciently strong to hold the arm Si!! in the notch of the cam |64 regardless of the driving reaction.

Referring now to Figs. 8 and 9 a modified form of the invention is disclosed. In this form the individual idler pinions 66 of liig. 3 and the cam and swinging arms are replaced by a single internalfexternal idler ring gear |66. The idler gear l66 is carried by a circular plate |62 to which itis secured. The plate |62 is mounted for rotation on an eccentric 56d which takes the place of the cam ltd, being driven by a gear |66 in the manner previously described. The

idler gear 66 meshes on its external portion with the driving pinions dii and 92 which in this form of the invention are so spaced as to have their peripheries equidistant from the center of the shaft 26. By slightly varying the proportions of the lgears of the driving trains illustrated in Fig. 2 and of the gears 96 andv 62,V the same ratios between the shaft Ell-and ring gear 36 may be provided with but a single gear A2 on the plate Sil'V which carries the orbit gear 36. The gear 42 meshes with the internal portion of the idler gear |66 on the opposite side of the shaft 26 from the point of engagement with. any one of the gears 9S and 92. vIn place'of the detent |92 ra gear 62" is rotatably mounted on theV dial sleeve H6 and is restrained against clockwise rotation by a pawl H32 pivoted on the transfer pinion shaft 24 and biased into engagement with the teeth of the gear 92 by a spring, not shown. Each of the gears il@ and ...2 are driven from their corresponding shafts through 9, inclusive, through roller clutches |66.

.In this form of the inventionthe operation is identical to that previously described except that during the., changeover from one ratio setting to the next'ad'jacent one, .two of the gears 96 or 92 will be in meshfwith the idler ring gear |66 at once.' The latter and the ring .gear 36 will be driven atthey speed of the faster one of the two gears, the roller clutch |66 of the slower gear or the detent |62 in the case of the gear 92' permitting the slower speed gear to rotate temporarily ahead of its driving shaft |-9. Due to the engagement of the idler gear S66 with gear 42 on the opposite side of the axis, theV output shaft in this modification will turn in the opposite direction to the input shaft.

This construction is particularly suitable for computing purposes wherein the control shaft |06 is connected to'be driven continuously for feeding in one variablervelocity, another variable velocity being fed in through the input yshaft 2e, the continuous product of these two variables appearing at the output shaft |32. In applications of this character it is also preferable to operate the control shaft |66 intermittently in ten steps per revolution; for example,

. by the use of a Geneva gear mechanism between shaft |60 and the shaft by which the latter is driven. Such a device is thus accurate to as many decimal places as there are stages of mechanism.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. A multiple ratio power transmission device comprising in combination an input shaft, an output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differ'4 ential may be controlled, and locking means and a piural" v ofdriving trains common to all of said di entials and capable cf selectively driving each of third members at any of sev eral speeds va1"'ing by equal increments from Zero input sha speed, said diferentiais having a speed reduction factor when the third member held stationary, equal to the number of speeds, including Zero, which the third members can be driven.

2. Amultiple ratio gear set for providing speed ratios in arithmetical progression in a number system having a given base number greater thanV 3. A multiple ratiopower transmission device l comprising in combination an input shaft, an output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, and means for controlling the speed of each of said third members in equal steps, including a cam associated with each differential.

4. A multiple ratio power transmission device comprising in combination an input shaft. an output shaft, a plurality ofv differentials connected in series between the input and output shafts and each vhaving a third member by the speed o-f which' the overall ratio of each differential may be controlled, and means for controlling the speed of each of said third members in equal steps', including a cam associated with each differential and arranged coaxially therewith.

5. A multiple ratio power transmission device comprising in combination an input shaft, an output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, means for controlling the speed of each of said third members in equal steps, the number of speeds, including zero, of each third member being equal to the reduction factor of each differential with the third member locked, the last-named means including a rotatable cam associated with each differential and transfer mechanism arranged between the cams of adjacent differentials.

6. A multiple ratio power transmission device comprising in combination an input shaft, an output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, means for controlling the speed of each of said third members in equal steps, the number of speeds, including zero, of each third member being equal to the reduction factor of each differential with the third member locked, the last-named means including a rotatable cam associated with each differential, transfer mechanism arranged between the cams of adjacent differentials, and an indicator driven with each cam, said indicators cooperating to show the ratio setting of the transmission as a whole.

'7. A multiple ratio power transmission device comprising in combination an input shaft, an output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, locking means and a' plurality of driving trains common to all of said differentials and capable of selectively drivingr each of said third members at any of several speeds varying by equal increments from Zero to input shaft speed, said driving trains including a series of shafts arranged around the differentials and parallel to the axis thereof,

8. A multiple ratio power transmission device comprising in combination an input shaft, an output shaft, a plurality of coaxial differentials con nected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, a plurality of driving trains connected to the input shaft and each including a shaft parallel to the axis of the differentials, and means for coupling each third member to any of said shafts independently of the other differentials,

9. A multiple ratio gear set for providing speed ratios in arithmetical progression in a number system having a base number greater than two, comprising a plurality of stages connected in series, one stage for each order of digits in the system, each stage including a planetary reduction gear having a reduction factor equal tothe base number and having three members two of which are connected to adjacent stages and means for selectively driving the third member of each planetary gear at any one of a number of speeds including zero which number is. equal to the base number.

10. A multiple ratio power transmission 4device comprising in combination an input shaft, an4

output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, locking means and a plurality of driving trains common to all of said differentials and capable of selectively driving each of said third members at any of several speeds varying by equal increments from zero to input shaft speed, said driving trains including a series of shafts arranged around the differentials and parallel to the axis thereof, gears carried by said shafts adjacent the third member of each stage, an idler gear for transmitting motion between said gears and said third member at each stage, and a carrier rotatable on the differential axis for positioning the idler gear to engage one or another of said gears.

11. A multiple ratio power transmission device comprising in combination an input shaft, an output shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, locking means and a plurality of driving trains common to all of said differentials and capable of selectively driving each of said third members at any of several speeds varying by equal increments from zero to input shaft speed, said driving trains including a series of shafts arranged around the differentials and parallel to the axis thereof, gears carried by said shafts adjacent the third member of each stage, an internal-external idler gear for transmitting motion between said gears and said third member at each stage, and an eccentric carrier rotatable on the differential axis for positioning the idler gear to engage one or another of said gears.

12. A multiple ratio power transmission device comprising in combination an input shaft, an outu put shaft, a plurality of differentials connected in series between the input and output shafts and each having a third member by the speed of which the overall ratio of each differential may be controlled, and means lor controlling the speed of each of said third members in equal steps, in` cluding a rotary member associated with each differential and arranged coaxially therewith for selective operation to different angular positions for different speed settings.

EDWIN L. ROSE. RALPH L. TWEEDALE. 

